1. Field of the Invention
The present invention relates to a toner manufacturing method.
2. Description of the Related Art
Energy saving is given as a problem of a printer or the like adopting an electrophotographic printing system, and a demand for a toner capable of being fixed at a low temperature, i.e., a toner having the so-called low temperature fixing performance, has increased.
In order to enable low temperature fixation, it has heretofore been known, as one of an effective method, to use a binding resin having a higher sharp melt performance as a toner. A polyester resin is superior as a binding resin having such a characteristic.
When a polyester resin is used as a binding resin for a toner, it is general to give an elastic modulus at a high temperature by advancing cross-linkage by using a cross-linker. Thereby hot offsets in fixation are prevented to control the toner not to have an excessive luster.
It is general to use a polycarboxylic acid of being trivalent or more as a cross-linker of the polyester resin (see, for example, Japanese Patent Application Laid-Open Publication No. H5-289401). Besides, a case of using hexamethylene tetramine or a polyvalent metal compound was disclosed (see, for example, Japanese Patent Application Laid-Open Publication No. H5-027478), but both of the disclosed materials have the problems of strong hydrophilicity at a cross-linkage point and the excessive humidity dependency of charging.
On the other hand, a technique of a hybrid resin aiming to have a heat characteristic close to that of a cross-linked resin was disclosed, which hybrid resin was produced by adding a radically polymerizable monomer, such as styrene, and a radical polymerization initiator to a polyester resin having a double bond, such as a fumaric acid unit, to make the polyester resin react with a part of a styrene resin.
However, the efficiency of the reaction of a double bond in a polyester resin and a radically polymerizable monomer, such as styrene, as described above, is low, and it is required to use a conventional polyester cross-linker in conjunction with the polyester resin practically in order to obtain an aimed elastic modulus characteristic, which fact remains as a problem.